Emily, with being a renter, I'd definitely check Pinterest for temporary solutions. I've seen DIYs where you can starch fabric to walls with an iron. Also try temporary wall paper/decals, but I'd test a small area first. Cabinet makers or even yourself would be able to create a flush vanity without attaching it to the wall. Plywood, especially hoop pine, has received a lot of traction. It really gives a clean, organic look that you could have custom cut to fit in the area. You could also use it on the wall – it could be stained, left natural, or painted for a feature. Have a look at EchoPanel. It is a decorative, acoustic pinboard that would add a splash of color/design. If it is above your vanity, you could pin pictures, inspirations, etc.

Emily, Don't particularly like dark colours in my own design but admire people that can make it work and I think the second photo has taken the room from plain to stunning, well done. I think you need some art on that wall though now?? Perhaps something steel, silver, it could make the room pop!!!

I agree with Brandi Nashi Hicks on timber and colours - think about providing colour with things that are simple to change like cushions, artwork, rugs and other accessories while keeping the basics of your home neutral - this way you can quickly, cheaply and easily change the look of your home as new trends or your tastes change. Don't worry too much about storage for when children come - the way you actually live in an apartment can vary drastically from how you think you'll live in it so put in what you need now, and then adapt your apartment to your family. Babies and small children don't need a lot of stuff - especially if you share cots, prams, clothing with friends and family so that you've got only what you need at that particular time - this works until they're at least school aged and provides a win/win solution to you and friends on storage and cost of little ones. Your future home looks as though it'll be a beautiful happy place to be a family and I hope you'll be very happy in it.

Have you thought about painting the walls in chalkboard paint,it comes in all colors and you could constantly change out the color and be inspired to chalk out whatever your design feels are at the time